While each source statement entered as part of a CL procedure is actually a CL command, the source can be divided into the basic parts used in many typical CL procedures.
- PGM command
- PGM PARM(&A)
Optional PGM command beginning the procedure and identifying any parameters received.
- Declare commands
- (DCL, DCLF, COPYRIGHT, DCLPRCOPT)
Mandatory declaration of procedure variables when variables are used, and optional definition of the size of the subroutine stack. The declare commands must precede all other commands except the PGM command.
- CL processing commands
- CHGVAR, SNDPGMMSG, OVRDBF, DLTF, …
CL commands used as source statements to manipulate constants or variables (this is a partial list).
- Logic control commands
- IF, THEN, ELSE, DO, ENDDO, DOWHILE, DOUNTIL, DOFOR, LEAVE, ITERATE,
GOTO, SELECT, ENDSELECT, WHEN, OTHERWISE, CALLSUBR, SUBR, RTNSUBR, ENDSUBR
Commands used to control processing within the CL procedure.
- Built-in functions
%SUBSTRING (%SST), %SWITCH, %BINARY (%BIN), %ADDRESS
(%ADDR), %OFFSET (%OFS)
Built-in functions and operators used in arithmetic, relational or logical expressions.
- Program control commands
- CALL, RETURN
CL commands used to pass control to other programs.
- Procedure control commands
- CALLPRC, RETURN
CL commands used to pass control to other procedures.
- ENDPGM command
- ENDPGM
Optional End Program command.
The sequence, combination, and extent of these components are determined by the logic and design of your application.
- A display file. Use display files to format information on a device display. If your procedure uses a display, you must enter and create the display file and record format by using the Create Display File (CRTDSPF) command before creating the module. You must declare it to the procedure in the declare section by using the Declare File (DCLF) command.
- A database file. Records in a database file may be read by a CL procedure. If your procedure uses a database file, the file must be created using the Create Physical File (CRTPF) command or the Create Logical File (CRTLF) command before the module is created. You can use Data Description Specifications (DDS), Structured Query Language (SQL), or interactive data definition utility (IDDU) to define the format of the records in the file. The file must also be declared to the procedure in the DCL section using the Declare File (DCLF) command.
- Other programs. If you use a CALL command, the called program must exist before running the CALL command. It does not have to exist when compiling the calling module.
- Other procedures. If you use the CALLPRC command, the called procedure must exist at the time CRTPGM is run. It does not have to exist when CRTCLMOD is run.